JP2012104434A - Fuel cell system, and method for operating fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system and a method for operating the fuel cell system capable of adjusting the supply of a gas fuel with high accuracy even if the environmental temperature varies.SOLUTION: The method for operating a fuel cell system 1 comprises the steps of determining a target value Ft for a flowmeter 3 with reference to the environmental temperature, and controlling a fuel supply unit 2 to supply a gas fuel to a reformer 5 so that the flowmeter 3 indicates the target value. Therefore a proper amount by mass of the fuel can be supplied according to the value of the output current of a fuel cell 6 regardless of whether the environmental temperature is high or low.

Description

  The present invention relates to a fuel cell system and a method for operating the fuel cell system.

  The fuel cell system supplies hydrogen-containing fuels such as city gas, liquefied natural gas (LPG), and kerosene to the reformer to generate hydrogen, and supplies hydrogen to the fuel electrode of the fuel cell stack.

  Usually, the flow rate of the gaseous fuel supplied to the fuel electrode of the fuel cell by the pump may vary depending on the environmental temperature when the amount of material is considered constant. For example, in the case of using a volume flow meter, if the temperature is cold, the concentration increases, so the volume flow is small, and if it is warm, the concentration is low, so the volume flow is large. Such a phenomenon results in a decrease in efficiency due to the concentration of the gaseous fuel in a cold region, or fuel depletion due to a decrease in the gaseous fuel in a warm region, resulting in damage to the fuel cell.

  Conventionally, as a technique in such a field, as described in Patent Document 1 below, a pump for supplying gaseous fuel to a fuel electrode of a fuel cell is provided, and a control instruction value (output control amount) for this pump is set near the pump. There is known a fuel cell system that corrects based on the ambient temperature (outside air temperature) and controls the pump with the corrected control instruction value to stabilize the supply amount even when the ambient temperature changes.

  In this system, for example, a reference value of a control instruction value at a certain environmental temperature is stored, and by multiplying the reference value by a ratio between the environmental temperature during operation of the system and the environmental temperature corresponding to the reference value, the gas The control instruction value is calculated based on the state equation.

JP 2004-207133 A

  However, when handling an actual gas, or in order to supply a gas supply amount determined based on the outside air temperature and the output current, as described in Patent Document 1, to the fuel cell or the like, the gas supply means The fuel cell system that directly adjusts the output does not take into account the accuracy and deterioration of the gas supply means, and thus there is a problem that the amount of gas actually supplied to the fuel cell or the like is not always accurate. .

  An object of the present invention is to provide a fuel cell system and a fuel cell system operating method capable of accurately adjusting the amount of gaseous fuel supplied even when the ambient temperature changes.

  A fuel cell system according to the present invention includes a reformer that generates a reformed gas containing hydrogen by a reforming reaction of a gaseous fuel, a fuel cell that generates power using the reformed gas, and a gaseous fuel in the reformer. The fuel supply means for supplying the fuel, the flow rate measuring means for measuring the flow rate of the gaseous fuel supplied to the reformer, the current value measuring means for measuring the current value of the output current of the fuel cell, and the environment for measuring the environmental temperature The temperature measurement means and the fuel substance amount per unit time to be supplied to the reformer according to the current value are stored in advance, and the gaseous fuel is supplied to the fuel supply means at a flow rate corresponding to the fuel substance quantity with reference to the environmental temperature. Control means for determining an instruction target value of the flow rate measurement means for discharging and controlling the fuel supply means so that the flow rate measurement means indicates the instruction target value.

  In addition, an operation method of the fuel cell system according to the present invention includes a reformer that generates a reformed gas containing hydrogen by a reforming reaction of a gaseous fuel, a fuel cell that generates power using the reformed gas, and a modification. A fuel supply means for supplying gaseous fuel to the gasifier, a flow rate measuring means for measuring the flow rate of the gaseous fuel supplied to the reformer, a current value measuring means for measuring the current value of the output current of the fuel cell, and the environment In a fuel cell system comprising an environmental temperature measuring means for measuring temperature and a control means for storing in advance a fuel substance amount corresponding to the current value, a unit per unit time to be supplied to the reformer according to the current value Determining a fuel substance amount; determining an indicated target value of a flow rate measuring means for discharging gaseous fuel to the fuel supply means at a flow rate corresponding to the fuel substance amount with reference to an environmental temperature; and a flow rate measuring means Indicates the indicated target value. Characterized in that it comprises Yo and controlling the fuel supply means.

  According to these fuel cell systems and fuel cell system operation methods, flow rate measurement is performed so that gaseous fuel having a flow rate corresponding to the amount of fuel material corresponding to the current value is discharged by the fuel supply means with reference to the environmental temperature. The indicated target value of the means is determined. Therefore, even when the environmental temperature changes, the amount of fuel material corresponding to the current value can be supplied to the reformer, and the supply amount of gaseous fuel can be adjusted with high accuracy.

  In the fuel cell system according to the present invention, it is preferable that the control means stores the aging deterioration information of the flow rate measurement means, and further determines the indicated target value by further referring to the stored aging deterioration information.

  Moreover, in the operating method of the fuel cell system according to the present invention, the control means stores aging deterioration information of the flow rate measurement means, and further includes a step of determining an instruction target value with reference to the aging deterioration information. preferable.

  According to these fuel cell systems and fuel cell system operation methods, even when the flow rate measuring means is deteriorated due to long-term use, the deterioration is added to the control of the fuel supply means. Therefore, the supply amount of gaseous fuel can be reliably adjusted without depending on the accuracy and deterioration of the fuel supply means, and the operation efficiency and long-term reliability of the system can be improved.

  Moreover, in the fuel cell system according to the present invention, it is preferable that the control means stores the cumulative value of the operation time of the flow rate measuring means as aged deterioration information.

  Further, in the operation method of the fuel cell system according to the present invention, the control means stores the accumulated value of the operation time of the flow rate measuring means as the aged deterioration information, and refers to the accumulated value of the operation time to determine the indicated target value. Preferably a step of determining is provided.

  According to these fuel cell systems and fuel cell system operation methods, the mechanical deterioration of the parts constituting the flow measurement means can be easily performed by using the cumulative value of the operation time of the flow measurement means as the aging deterioration information. Since it can be estimated, the supply amount of gaseous fuel can be adjusted more accurately.

  In the fuel cell system according to the present invention, the control means preferably stores a cumulative value of the flow rate measured by the flow rate measurement means as aged deterioration information.

  In the operation method of the fuel cell system according to the present invention, the control means stores the accumulated value of the flow rate measured by the flow rate measuring means as the aged deterioration information, and the accumulated value of the flow rate measured by the flow rate measuring means. It is preferable to comprise the step of determining the indicated target value with reference to FIG.

  According to these fuel cell systems and fuel cell system operation methods, the accumulated value of the flow rate measured by the flow rate measurement unit is used as the aged deterioration information, so that the flow rate measurement unit by accumulation of impurities contained in the gaseous fuel can be used. Since the aged deterioration state can be easily estimated, the supply amount of the gaseous fuel can be adjusted with higher accuracy.

  In the fuel cell system according to the present invention, it is preferable that the control means stores the instruction target value as a map and determines the instruction target value based on the map.

  In the operation method of the fuel cell system according to the present invention, it is preferable that the control means further includes a step of storing the indicated target value as a map and determining the indicated target value based on the map.

  According to these fuel cell systems and fuel cell system operation methods, control corresponding to the environmental temperature and current values measured by the environmental temperature measuring means and the current value measuring means, respectively, or the aged deterioration information of the flow rate measuring means, respectively. The calculation load can be further reduced by selecting the instruction value from the map.

  Moreover, as a structure which exhibits the said effect | action more effectively, the structure whose flow volume measuring means is a flow volume measuring means based on a volume is mentioned.

  According to the present invention, even when the environmental temperature changes, it is possible to accurately adjust the supply amount of gaseous fuel.

1 is a block diagram schematically showing one embodiment of a fuel cell system according to the present invention. It is a flowchart which shows the control procedure in a fuel cell system. It is a figure which shows the map of the cumulative value of the operation time of a flow measurement means. It is a flowchart which shows the control procedure in 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the fuel cell system 1 of the present embodiment includes a reformer 5 that generates a reformed gas containing hydrogen using gaseous fuel, and a solid oxide that generates power using the reformed gas. A physical fuel cell 6.

  The reformer 5 contains a reforming catalyst therein and generates a reformed gas by a reforming reaction such as steam reforming, partial oxidation reforming, or autothermal reforming. A known catalyst can be used as the reforming catalyst.

  The gaseous fuel is a hydrocarbon-based fuel known in the field of solid oxide fuel cells as a raw material for reformed gas, that is, a compound containing carbon and hydrogen in its molecule (containing other elements such as oxygen). Or a mixture thereof may be used as appropriate. For example, it is a compound containing carbon and hydrogen in the molecule, such as hydrocarbons, alcohols and ethers. More specifically, methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), city gas, hydrocarbons such as gasoline, naphtha, kerosene and light oil, alcohols such as methanol and ethanol, dimethyl ether, etc. Ethers and the like. Of these, kerosene and LPG are preferable because they are easily available. Moreover, since kerosene and LPG can be stored independently, they are useful in areas where city gas lines are not widespread. Furthermore, a solid oxide fuel cell using kerosene or LPG is useful as an emergency power source. In addition, in the case of the fuel which is liquid at normal temperature, it can be used as gaseous fuel, for example by vaporizing with a vaporizer.

  The fuel cell 6 uses the reformed gas generated by the reformer 5 as fuel, and generates power with a cell stack formed by connecting a plurality of cells called SOFC (Solid Oxide Fuel Cells) in series. Each cell is configured by disposing an electrolyte, which is a solid oxide, between a fuel electrode and an air electrode. The electrolyte is made of, for example, yttria stabilized zirconia (YSZ), and conducts oxide ions at a temperature of 800 ° C. to 1000 ° C. The fuel electrode is made of, for example, a mixture of nickel and YSZ, and generates electrons and water by reacting oxide ions with hydrogen in the reformed gas supplied to the fuel electrode. The air electrode is made of, for example, lanthanum strontium manganite, and reacts oxygen in the air supplied to the air electrode with electrons to generate oxide ions.

  The fuel cell system 1 includes a fuel supply device 2 that supplies gaseous fuel to the reformer 5, a flow rate measuring device 3 that measures the flow rate of the gaseous fuel supplied to the reformer 5 by the fuel supply device 2, A current value measuring device 7 that measures the current value of the output current of the fuel cell 6 and an environmental temperature measuring device 8 that measures the environmental temperature are provided. Furthermore, the fuel cell system 1 includes a control device 4 that controls the fuel supply device 2 based on the current value measured by the current value measuring device 7 and the environmental temperature measured by the environmental temperature measuring device 8.

  Here, the environmental temperature is the outside air temperature in the environment where the fuel cell system 1 is installed. Furthermore, the amount of fuel substance used in the following description is the number of moles or mass per unit time of the gaseous fuel supplied to the reformer 5 by the fuel supply device 2.

  The fuel supply device 2 has a pump for supplying gaseous fuel to the reformer 5. The fuel supply device 2 performs feedback control so that a value acquired by a flow rate measuring unit 3 to be described later becomes a flow rate corresponding to the amount of fuel material per unit time of gaseous fuel to be supplied to the reformer 5, Gaseous fuel is supplied to the reformer 5.

  The fuel supply device 2 outputs information indicating that it is in operation to the control device 4 during operation of the pump. In addition to the pump, the fuel supply device 2 has a control valve or the like provided in the gas fuel supply line.

  The flow rate measuring device 3 has a flow meter provided in a gaseous fuel supply line. The flow rate measuring device 3 measures the flow rate of the gaseous fuel based on the volume, and outputs a measured value of the flow rate to the control device 4. Here, the measurement accuracy of the flow rate by the flow rate measuring device 3 is small and highly accurate in the initial stage of use. However, as the service life becomes longer, mechanical deterioration of parts constituting the flow rate measuring device 3 or The measurement accuracy tends to decrease due to deterioration caused by adhesion of impurities contained in the gaseous fuel to the flow path.

  The current value measuring device 7 has an ammeter that measures the sweep current value in the fuel cell 6, and outputs the measured sweep current value to the control device 4.

  The environmental temperature measuring device 8 has a thermometer that measures the environmental temperature. Specifically, this thermometer is installed around the fuel supply device 2, measures the temperature around the fuel supply device 2, and outputs the measured environmental temperature to the control device 4.

  The control device 4 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, and the like, and controls the entire system of the fuel cell system 1. Is. That is, the control device 4 controls the amount of power generated in the fuel cell 6 (for example, current sweep from the fuel cell 6). Further, the control device 4 sets the sweep current value I output from the current measuring device 7, the environmental temperature K output from the environmental temperature measuring device 8, and the actual flow rate Fa of the gaseous fuel output from the flow rate measuring device 3. Get each. And the fuel supply apparatus 2 is controlled by performing a predetermined | prescribed process based on each acquired information.

  The control device 4 stores in advance a fuel material amount of gaseous fuel to be supplied to the reformer 5 according to the sweep current value. Therefore, the control device 4 can determine the fuel material amount Nf of the gaseous fuel necessary for power generation by acquiring the sweep current I acquired from the current measuring device 7. Note that the amount of fuel substance corresponding to the sweep current value may be stored as a calculation formula, or a suitable value obtained experimentally may be stored as a map.

  Further, the control device 4 refers to the environmental temperature K acquired from the environmental temperature measurement device 8 and determines the instruction target value Ft of the flow rate measurement device 3. The instruction target value may be calculated each time using the gas equation of state, or a suitable instruction target value of the flow rate measuring device is stored in advance as a map for each environmental temperature, and the instruction target value is indicated with reference to the map. A target value may be determined.

  Further, the control device 4 compares the actual fuel flow rate Fa discharged from the fuel supply device 2 acquired from the flow measurement device 3 with the indicated target value Ft of the flow measurement device 3. Then, the control device 4 controls the fuel supply device 2 so that the actual fuel flow rate Fa is equal to the indicated target value Ft. Specifically, when the actual fuel flow rate Fa is smaller than the command target value Ft, the discharge amount of the fuel supply device 2 is increased. Conversely, when the actual fuel flow rate Fa is larger than the command target value Ft, the fuel supply device 2 The fuel supply device 2 is controlled so as to reduce the discharge amount.

  Although not shown, the fuel cell system 1 includes a water vapor supply device that supplies water vapor to the reformer 5 and an air supply device that supplies air to the air electrode of the fuel cell 6. The steam supply apparatus vaporizes water by a vaporizer provided integrally with the reformer 5 or separately from the reformer 5 and supplies the water to the reformer 5 as steam.

  Next, functions of the control device 4 in this embodiment will be described. FIG. 2 is a flowchart of processing executed by the control device 4 when the fuel cell system is started and power generation is started in the first embodiment. Each process shown in FIG. 2 is repeatedly executed by the control device 4 during normal operation of the fuel cell system 1.

  First, the control device 4 acquires the sweep current value I (S1), and determines the fuel substance amount Nf per unit time to be supplied to the reformer 5 at the acquired sweep current value I (S2).

  Next, the environmental temperature K is acquired (S3), and a desired flow rate X corresponding to the fuel substance amount Nf is determined at the temperature (S4). Then, the instruction target value Ft of the flow rate measuring device 3 for discharging the gaseous fuel to the fuel supply device 2 at the desired flow rate is determined (S5).

  Next, the control device 4 acquires the fuel flow rate Fa supplied to the current reformer 5 (S6) and compares it with the indicated target value Ft (S7). If the current fuel flow rate Fa is equal to the command target value Ft, the process returns to step S1 and the processes of steps S1 to S7 are repeated. On the other hand, if the current fuel flow rate Fa and the command target value Ft are not equal, the output of the fuel supply device 2 is adjusted (S8). Specifically, the control device 4 controls the fuel supply device 2 to increase the discharge amount of the fuel supply device 2 when Fa <Ft, and decreases the discharge amount of the fuel supply device 2 when Fa> Ft. Thus, the fuel supply device 2 is controlled. Then, the process returns to step S6, and the current fuel flow rate Fa is acquired again and compared with the instruction target value Ft.

  According to the fuel cell system 1 and the operation method of the fuel cell system 1 of the present embodiment, the flow meter instruction target value Ft of the flow measurement device 3 is determined with reference to the environmental temperature, and the flow measurement device 3 determines the flow meter instruction target. Since the fuel supply device 2 is controlled so as to show the value and the gaseous fuel is supplied to the reformer 5, the amount of fuel substance corresponding to the current value of the output current of the fuel cell 6 regardless of the environmental temperature is high or low. Fuel supply becomes possible.

  Moreover, since the setting of the control instruction value based on the environmental temperature can be stored in advance as a map, in addition to the value obtained from the mathematical formula, a more preferable value obtained experimentally can be stored. This can be realized with a low computational load. Therefore, even when the environmental temperature changes, it is possible to accurately adjust the supply amount of the gaseous fuel while reducing the calculation load.

[Second Embodiment]
The fuel cell system of the second embodiment has the same configuration as the fuel cell system 1 shown in FIG. 1, but the control device 4 further stores aging deterioration information of the flow rate measuring device 3. Further, the processing in the control device 4 is different from that in the first embodiment. In this embodiment, when determining the instruction | indication target value of the flow measuring device 3, it has a process which considers the aged deterioration information of the flow measuring device 3. FIG. Specifically, a cumulative value of the operation time of the flow rate measuring device 3 is used as the aging deterioration information. FIG. 3 is a map showing the relationship between the fuel discharge amount taking the aging deterioration information into consideration and the flow rate measuring device 3 indicated value. FIG. 4 is a flowchart of processing executed by the control device 4 when the fuel cell system is started and power generation is started in the present embodiment. Each process shown in FIG. 4 is repeatedly executed by the control device 4 during normal operation of the fuel cell system.

  As shown in FIG. 4, the control device 4 acquires the environmental temperature K (S3), determines a desired flow rate X corresponding to the fuel substance amount Nf at the temperature, and then the cumulative operation time of the flow measurement device 3 t is acquired (S9). The control device 4 selects a map that is aged deterioration information from the accumulated operation time t of the flow rate measuring device 3. Specifically, when the desired fuel flow rate determined from the sweep current value I, the required fuel material amount Nf and the environmental temperature K is X1, refer to the map M1 when 0 year ≦ t year <3 years. (S10 to S11A), the instruction target value X1 is determined (S5A). In the case of 3 years ≦ t year <5 years, the map M2 is referred to (S10 to S11B), and the instruction target value Ft is determined to be X2 (S5B). If 5 years ≦ t year <6 years, the map M3 is referred to (S10 to S11C), and the instruction target value Ft is determined to be X3 (S5C). Hereinafter, as in the first embodiment, the current fuel flow rate Fa is compared with the indicated target value Ft.

  According to the fuel cell system and the operation method of the fuel cell system of the present embodiment, mechanical deterioration of parts constituting the flow rate measuring device 3 caused by long-term use of the flow rate measuring device 3 and impurities contained in the fuel are present. The instruction target value Ft can be determined in consideration of an error between the instruction value of the flow rate measuring device 3 and the actual discharge amount due to deterioration due to accumulation in the flow path. As a result, the supply amount of gaseous fuel can be adjusted with high precision, and the system operation efficiency and long-term reliability can be improved to ensure a long-term life.

  In the above-described embodiment, the graph format map is used for explanation, but a matrix format map may be used. In addition, even if the aged deterioration information acquired in step S9 is not the accumulated operation time of the flow rate measuring device 3, but the accumulated value of the flow rate of the flow rate measuring device 3, the same effect as described above can be obtained.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, in the above embodiment, the case of using a solid oxide fuel cell has been described, but the present invention can also be applied to a fuel cell system using a solid polymer fuel cell or a molten carbonate fuel cell.

  In the operation methods in the above embodiments, the case where the flow rate measurement value is returned to step S6 after step S8 is followed by the flow rate measurement value has been described. However, step S1 for acquiring the sweep current value and the environment You may return to step S3 which acquires temperature.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel supply apparatus (fuel supply means), 3 ... Flow measurement apparatus (flow measurement means), 4 ... Control apparatus (control means), 5 ... Reformer, 6 ... Fuel cell, 7 ... Current value measuring device (current value measuring means), 8... Environmental temperature measuring device (environment temperature measuring means).

Claims (11)

A reformer that generates reformed gas containing hydrogen by a reforming reaction of gaseous fuel;
A fuel cell that generates power using the reformed gas;
Fuel supply means for supplying the gaseous fuel to the reformer;
Flow rate measuring means for measuring the flow rate of the gaseous fuel supplied to the reformer;
Current value measuring means for measuring the current value of the output current of the fuel cell;
Environmental temperature measuring means for measuring environmental temperature;
A fuel material amount per unit time to be supplied to the reformer according to the current value is stored in advance, and the fuel supply means supplies the gaseous fuel at a flow rate corresponding to the fuel material amount with reference to the environmental temperature. A fuel cell system comprising: control means for determining an instruction target value of the flow rate measurement means for causing the flow rate measurement means to discharge, and controlling the fuel supply means so that the flow rate measurement means indicates the instruction target value .   2. The fuel cell according to claim 1, wherein the control means stores aging deterioration information of the flow rate measuring means, and further determines the indicated target value by further referring to the stored aging deterioration information. system.   3. The fuel cell system according to claim 2, wherein the control unit stores an accumulated value of an operation time of the flow rate measuring unit as the aging deterioration information.   3. The fuel cell system according to claim 2, wherein the control unit stores a cumulative value of the flow rate measured by the flow rate measurement unit as the aging deterioration information.   The fuel cell system according to any one of claims 1 to 4, wherein the control means stores the indicated target value as a map, and determines the indicated target value based on the map. .   The fuel cell system according to any one of claims 1 to 5, wherein the flow rate measurement unit is a volume-based flow rate measurement unit. A reformer that generates reformed gas containing hydrogen by a reforming reaction of gaseous fuel;
A fuel cell that generates power using the reformed gas;
Fuel supply means for supplying the gaseous fuel to the reformer;
Flow rate measuring means for measuring the flow rate of the gaseous fuel supplied to the reformer;
Current value measuring means for measuring the current value of the output current of the fuel cell;
Environmental temperature measuring means for measuring environmental temperature;
A fuel cell system comprising: a control unit that stores in advance a fuel substance amount corresponding to the current value;
Determining the amount of the fuel material per unit time to be supplied to the reformer according to the current value;
Determining an instruction target value of the flow rate measuring means for discharging the gaseous fuel to the fuel supply means at a flow rate corresponding to the fuel substance amount with reference to the environmental temperature;
And a step of controlling the fuel supply means so that the flow rate measuring means indicates the indicated target value. The control means stores aged deterioration information of the flow rate measuring means,
8. The method of operating a fuel cell system according to claim 7, further comprising a step of determining the indicated target value with reference to the aged deterioration information. The control means stores a cumulative value of operation time of the flow rate measuring means as the aging deterioration information,
The operation method of the fuel cell system according to claim 8, further comprising a step of determining the indicated target value with reference to a cumulative value of the operation time. The control means stores a cumulative value of the flow rate measured by the flow rate measurement means as the aging deterioration information,
9. The method of operating a fuel cell system according to claim 8, further comprising the step of determining the indicated target value with reference to a cumulative value of the flow rate measured by the flow rate measuring means. The control means further stores the indicated target value as a map,
The method for operating a fuel cell system according to any one of claims 7 to 10, further comprising a step of determining the indicated target value based on the map.

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